1. Field of the Invention
The present invention relates to a triode carbon nanotube field emission display using a barrier rib structure and a manufacturing method thereof.
2. Description of the Related Art
FIG. 1 is a sectional view schematically showing the structure of a conventional field emission display (FED). Referring to FIG. 1, the conventional FED includes transparent front and rear substrates 5 and 1 with a spacer 8 therebetween for separating the front and rear substrates 5 and 1 by a predetermined gap. Cathodes 2 are formed on the rear substrate 1 in a striped pattern. An insulating layer 3 is formed on the cathodes 2. Gates 4 are formed on the insulating layer 3 in a striped pattern crossing the cathodes 2. Holes 3xe2x80x2 are formed in the insulating layer 3 on the cathodes 2. Microtips 2xe2x80x2 for emitting electrons are formed on the cathodes 2 exposed by the holes 3xe2x80x2. The gates 4 are provided with opening portions 4xe2x80x2 corresponding to the holes 3xe2x80x2 so as to allow the electrons from the microtips 2xe2x80x2 to be emitted to anodes 6. The anodes 6 are formed on the surface of the front substrate 5 facing the rear substrate 1 in a striped pattern crossing the cathodes 2. The anodes 6 are coated with luminescent material layers 7. The electrons emitted from the microtips 2xe2x80x2 strike the material layers 7, thereby emitting light.
FIG. 2 is a sectional view of a conventional FED employing a mesh grid. Similarly to the FED of FIG. 1, the conventional FED of FIG. 2 includes transparent front and rear substrates 15 and 11 with a spacer 18 therebetween for separating the front and rear substrates 15 and 11 by a predetermined gap. Cathodes 12 formed in a striped pattern, an insulating layer 13, and gates 14 formed in a striped pattern crossing the cathodes 12 are sequentially provided on the rear substrate 11. Holes 13xe2x80x2 are formed in the insulating layer 13 on the cathodes 12. Microtips 12xe2x80x2 are formed on the cathodes 12 exposed by the holes 13xe2x80x2. The gates 14 are provided with opening portions 14xe2x80x2 corresponding to the holes 13xe2x80x2. The anodes 16 are formed on the surface of the front substrate 15 facing the rear substrate 11 in a striped pattern crossing the cathodes 12. The anodes 16 are coated with luminescent material layers 17. The FED of FIG. 2 also includes a metal mesh grid 19, which controls electrons emitted from the microtips 12xe2x80x2, between the gates 14 and the anodes 16.
In manufacturing triode FEDs without using a photolithography method, a mesh coated with an electrode may be used as a gate electrode. However, when a mesh structure is provided to a FED panel which is formed of glass and has a high vacuum inner side, mechanical stress increases, and thus a spacer may be warped while a front substrate and a rear substrate are sealed, or the front and rear substrates may be broken due to atmospheric pressure during vacuum exhaust. In other words, since a mesh structure and a spacer are integrally formed in a conventional FED, warp of the mesh structure due to thermal expansion or gas flow horizontally presses the spacer. Accordingly, the spacer which is resistant to a vertical pressure but weak to a horizontal pressure diverges from an originally designed position or is warped, and thus it may eventually break due to a vertical atmospheric pressure. This makes it very difficult to manufacture FED panels.
To solve the above problem, an object of the present invention is to provide a triode carbon nanotube field emission display (FED) using a barrier rib structure and a manufacturing method thereof, for preventing damage or warping due to thermal expansion of a mesh structure by forming barriers on a cathode pattern using a screen printing method and mounting the mesh structure on the barriers to stably fix the mesh structure and a spacer within a panel.
To achieve the above object, the present invention provides a carbon nanotube FED including front and rear substrates disposed to face each other and be separated by a predetermined gap, cathodes formed on the rear substrate in a striped pattern, barrier ribs formed on the cathodes to a predetermined thickness at predetermined intervals so as to expose the cathodes at predetermined intervals, carbon nanotubes formed on the cathodes exposed by the barrier ribs, for the emission of electrons, a mesh structure mounted on the barrier ribs, which includes opening portions for passing electrons emitted from the carbon nanotubes and slots in a region corresponding to gaps between the barrier ribs, spacers for keeping a predetermined gap between the front and rear substrates, each of the spacers being shaped into a rugged bar having protrusions which are inserted between the barrier ribs through the slots, anodes formed on the front substrate in a striped pattern crossing the cathodes, and luminescent material layers deposited on the anodes.
Each of the barrier ribs is formed between portions at which the cathodes and anodes cross to a thickness of 10-100 xcexcm. The barrier ribs are formed in a region corresponding to the black matrix of the anodes. The mesh structure is formed of an insulator, and gates are formed on the mesh structure in a striped pattern crossing the cathodes.
The mesh structure may be formed of a conductive material to be wired as a common electrode. The size of each opening portion of the mesh structure is determined in accordance with the area of a portion at which each cathode and each anode cross. The width of each protrusion of the spacer toward the cathodes is narrower than the gap between the barrier ribs by 5-10 xcexcm.
To achieve the above object, the present invention provides a method for manufacturing a carbon nanotube field emission display including front and rear substrates disposed to face each other and be separated by a predetermined gap, cathodes formed on the rear substrate in the pattern of stripes, barrier ribs formed on the cathodes to a predetermined thickness at predetermined intervals so as to expose the cathodes at predetermined intervals, carbon nanotubes formed on the cathodes exposed by the barrier ribs, for the emission of electrons. a mesh structure mounted on the barrier ribs, which includes opening portions for passing electrons emitted from the carbon nanotubes and slots in a region corresponding to gaps between the barrier ribs, spacers for maintaining a predetermined gap between the front and rear substrates, each of the spacers being shaped into a rugged bar having protrusions which are inserted between the barrier ribs through the slots, anodes formed on the front substrate in a striped pattern crossing the cathodes, and luminescent material layers deposited on the anodes. The method includes the steps of (a) forming the barrier ribs on the rear substrate having the cathodes in a striped pattern, (b) depositing the carbon nanotubes on the cathodes between the barrier ribs to form electron emission sources, (c) mounting the mesh structure on the barrier ribs, (d) inserting the spacers between the barrier ribs through the slots of the mesh structure, and (e) mounting the front substrate having the anodes coated with the luminescent material layers on the spacers such that the anodes are accurately aligned and performing a sealing process.
In the step (a), each of the barrier ribs is formed to a thickness of 10-100 xcexcm. The step (b) is performed by one of a screen printing method, a chemical vapor deposition method, an electrophoretic method and an anodized alumina sheet cathode method. In the step (c), the mesh structure is formed of an insulator, and the step (c) includes the step of forming gates on the mesh structure in a striped pattern crossing the cathodes. The mesh structure may be formed of a conductive material. In the step (c), the size of each opening portion of the mesh structure is determined in accordance with the area of a portion at which each cathode and each anode cross. In the step (d), the width of each protrusion of the spacer toward the cathodes is narrower than the gap between the barrier ribs by 5-10 xcexcm. The barrier ribs, the opening portions and slots of the mesh structure and the protrusions of the spacers are designed such that the front substrate, the mesh structure and the spacers are assembled by self-alignment.